Cement manufacture



Aug? 1938. N. AHLMANN 2,125,263

CEMENT MANUFACTURE Filed Feb. 9, 1937 2 Sheets-Sheet l ATTORNEY} Aug. 2,,1938. I N. AHLMANN 3 CEMENT MANUFACTURE Filed Feb. 9, 1937 2 Sheets-Sheet 2 l i INVENTOR ATTORNEY;

Patented Aug. 2, 1938 mural) STATES PATENT orrlca CEMENT MANUFACTURE Nikolai Ahlmann, Copenhagen, Denmark, assignor to F. L. Smidth & Company, New York, N. Y., a corporation of New Jersey Application February 9, 1937, Serial No. 124,821 In Great Britain February 11,1936

2 Claims. (Cl. 263-53) This invention relates to the manufacture of practice in the drying of cement slurry, the drycement and is concerned more particularly with log is carried on by means of waste gases from a novel method and apparatus for the treatment the kiln and the nodules and gases maybe adof the raw material in the form of slurry to place vantageously brought into contact with one an- 5 it in condition for calcination, sintering, or both. other in a drier interposed between the noduliz- 5 In the production of cement, as, for example, ing device and the kiln, or, if desired, the drying by the wet process, the raw material slurry must may take place in the kiln itself, as, for example, be dried prior to the burning operation and econin an enlarged chamber at the inlet end of the cmy in manufacture requires that the drying be kiln.

carried on as eiliciently as possible. When the For a better understanding of the invention, 10 raw materials are burned in a rotary kiln, large reference may be had to the accompanying drawamounts of waste gases are available for drying ings in which purposes, and when the slurry is dried by that Figure l is aview, partly in elevation and partly heating medium, the surfaces of contact between in section, showing apparatus suitable for the is the slurry and the hot gases should be as large arrying on of the new method;

as possible for efiiciency and economy. How- Figure 2 is a similar view of another form of ever, those forms of drying apparatus utilizing apparatus; waste gases, which give the best results with Figure 3 is a sectional view on the line 3-3 of respect to heat economy, have mechanical dis- Figure 2;

advantages, in that they ordinarily include a con- Figure 4 is a sectional view on the line 4-4 of 20 siderable amount of heavy movable bodies, such Figure 5, of a modified form of apparatus generas chains and the like, and in their operation, ally similar to that illustrated in Figure 2; and they also have a substantial power consumption. Figure 5 is a sectional view on the line 55 of v The formation of the slurry into nodules, which Figure 4.

are then subjected to the action of the hot gases, Referring to the drawings, that form of appa- 25 ives satisfactory results because the total surratus illustrated in F re 1 i c udes a nodulizface of the material to be dried is thereby renv ing device lll which may be of any suitable condered large and eflicient heat exchange can be struction, as, for example, it may consist of a obtained. However, as raw slurry is ordinarily otary drum or may be devices similar to those too wet to be nodulized, it has been necessary disclosed in the patents to Nielsen No. 1,892,074, 30

heretofore to dry it to some extent before the December 27, 1032, or Fasting No. 1,980,130, Nonodulization takes place, and this drying operavember 6, 1934. The raw slurry is introduced tion is an expensive one for'the reasons above into the nodulizing device through an inlet conpointed out. V duit II, and the nodules produced in the device The present invention is, accordingly, directed are delivered to adrier i2. The nodules may be 35 to the provision of a method and apparatus by conveyed to the drier in any suitable manner, which the nodulization and drying of the slurry as, for example, the device may discharge into can be carried on with increased efliciency and a hopper l3 which may be so constructedas to economy over those previously obtained. In the p ven t es p of the gases from he drier- 40 practice of the invention, a relatively small quan- The drier may be of any suitable type but that 40 tity of the slurry is dried to the extent necessary illustrated consists of a. vertical shaft ll of any to permit its formation into nodules and it is suitable construction containing a plurality of thereafter nodulized and dried. The hot dry louvres l5 so arra ed t at th odules pas nodules are then returned for addition to raw down through the shaft are exposed to the action wet slurry to form amixture suitable for nodulizof the hot gases passing upward through the 45 ing, and the nodules so produced are dried. A drier. These gases are delivered to the bottom.

. portion of the dried nodules is then delivered to of the shaft through the inlet duct l6 and withthe kiln for burning while the remainder lgredrawn through the outlet duct l1 connected to turned and employed for mixture ith raw r the suction fan l8. At the bottom of the drier,

'Thus, once the process is started, it may be conthe nodules are delivered upon a jigging screen 50 tinued indefinitelyand no drying of the raw mais by which part of the dried nodules is sepaterials in the form of slurry is required, except rated from the remainder. The finer nodules in the preparation of the quantity of nodules first passing through the screen are collected in a made. s hopper 20 and delivered to a conveyor 2| which In theapplication of the inventionin actual in turn delivers them to an elevator 22. The

40 fed thereto.

nodules discharged from the elevator enter' a hopper 23 from which they are discharged the nodulizing device to be mixed with the raw slurry entering through the conduit H. The

5 larger dried nodules are delivered from the screen to a hopper 24 which leads through the hood 25 and dischargesthenodules in the upper end of the rotary kiin-26. The gases passing from the kiln enter the hood to which the duct l6 iscon 10 nected.

In the operation of the apparatus, a quantity of raw wet slurry is dried to place it in condition for nodulization, nodules are'formed therefrom, and the nodules are dried. These nodules are not delivered to the kiln, but are used for mixing with raw wet slurry to produce a mixture suitable for nodulizing. The nodulizing operation is then carried on in the usual way, and the nodules formed of the mixture are dried and separated into two portions, one of which is delivered to the kiln and the other of which is returned to the nodulizing apparatus for mixture with the incoming raw slurry. Accordingly, once the process is started, no further drying of the raw materials in the form of slurry is required, and

the entire drying operation is carried on with respect to nodular materials. The drying operation is thus highly eflicient.

By the use of the screen to separate that part of the dried nodules that is to be returned from the part that is delivered to the kiln, the dust is removed from the kiln feed and the burning process is thus facilitated Moreover, it is found that the finer nodules and dust are more suitable 5 than the larger nodules for mixing with the raw 5 izing. The quantity of nodules used for the purpose thus depends on the condition of the raw slurry, as, for example, if. 162 parts of raw slurry containing 62 parts of water and 100 parts of dry material are supplied to the nodulizing device, it

56 has been found that by the addition of about 182 parts of dry hotfine nodules, a mixture is produced :which' canbe easiiy nodulized and the nodules formed from the mixture may be readily dried without deterioration in their quality with 55 respect to burning. The nodulizing operation may be controlled in various ways, and preferably, the control is effected by regulating the amount of raw slurry fedto the nodulizing device, since the size 'of the nodules and the amount of the 60 material that passes through the screen and is thereby returned to the device depend on the rela-,-

tive quantities of dried nodules and raw slurry acted on-therein. I While the apparatus illustrated in Figure 1 is 65 suitable for the performance of the new method,

it will be understood that" changes may be made in the apparatus as desired. For example, instead of using a louvre type drier, a bail drier may be employed. Also, instead of .using a drier 70 which isinterposedbetween the nodulizingdevice and the kiln as a separate piece of apparatus, the drying of, the nodules may be carried on in-the entrance end of the kiln itself. Constructions of the latteritype are illustrated in "the v (5 remaining figures of the drawings.

In that form of apparatus illustrated in Figure 2, the kiln, generally designated 27, is provided with an enlarged chamber 28 at its inlet end. This chamber includes a cylindrical screen 29 mounted for rotation with thekiln and having its interior in communication with the interior of the kiln. The nodulizing device 30, which is illustrated, is of the type shown in the copending applieation of Middelboe, Serial No. 73,411, filed April 9, 1936, although any other suitable nodulizing device, such as that illustrated in Figure 1,

may be employed. The nodules discharged from the device enter a hopper 3| leading to a conveyor 32 which enters the chamber 28 and extends into the interior of the screen 29. This conveyor lies within a trough 33, the open top of which lies close to the screen 29,. and, in the operation of the conveyor, the nodules are discharged upon the interior of the screen by the conveyor and are held in place thereon by the hot, gases leaving the kiln and passing outwardly through the screen.

When the nodules have been carried around with the screen through almost a complete rota- ,tion thereof, they are brought beneath an inverted trough 34 which lies outside the screen 9 within the chamber 28 and is supplied with air under pressure through a duct 35. The blast of air discharged upon the screen from the trough releases the nodules and they drop into a sloping trough 36 which delivers them into the upper end of the kiln. At this end, the kiln isprovided with a plurality of screens 31 spaced angularly about the kiln, the portion of the kiln containing the screens heing enclosed within a circumferential chamber 38 from the lower part of which leads a eonduit 39. .Such of the finer nodules as pass through the screens 31 are delivered through the conduit?! to a conveyor 40 which leads to an elevator 2| by which the nodules are returned to the nodulizing device where they are mixed with the raw slurry being fed'thereto. The hot gases which leave the chamber 28 after passing through the screen 29 are carried off through the duct 42.

The apparatus illustrated in Figure 4 is gen= erally similar to that shown in Figure 2, and in- I cludes a drying chamber 28 at the end of the kiln within which is a cylindrical screen. 29 rotated by the-kiln. The nodules from the nodulizing device are delivered upon the screen and, discharged upon the inner surface thereof by a conveyor 32 and are released from the screen by the action of an air blast directed thereon from the trough 34. The nodules released from the screen are collected in a trough 43 which contains a screw conveyor 44, part of the flights of which are right hand and the remainder left hand. Those noduies'which enter the forward part of the trough 43 are carried out through the trough to the conduit 45, by which they are delivered to a conveyor 40 and returned by .an elevator 4| to the nodulizing device. The remainder of the nodules, which are picked up by the other flights of the screw 44 are delivered directly into the end of the kiln 5.

With the construction described, no changes in a and the advantages of drying the material in menses nodular form are obtained without the necessity of any substantial drying of slurry prior to nodulization. While specific forms of nodulizing de-' vices and driers have been shown and described for purposesof explanation, it will be apparent that the utility of the new method is not dependent upon the use of apparatus of any particular type, and those shown are tobe understood merely as typical of numerous devices appropriate for the purpose.

I claim:

1. In the manufacture of cement the method which comprises formingslurry into nodules of suflicient size to be satisfactorily burned in a kiln to produce cement clinker, subjecting such nodules to a drying treatment, passing a part of the said nodules which have been subjected to the drying treatment to a kiln for burning, and mixing another part of the said nodles which have been subjected to the drying treatment with fresh slurry which is too wet to be formed into nodules to form a composite mixture capable of being formed into nodules.

2. In the manufacture of cement, the method which comprises forming slurry into nodules of sumcient size to be satisfactorily burned in a kiln to produce cement clinker, and mixing a portion of the said nodules with fresh slurry which is too wet to be formed into nodules to form a composite mixture capable of being formed into nodules.

NIKOLAI AHLMANN. 

